Impact tool



May 30, 1967 D. K. SKOOG IMPACT TOOL 2' Sheets-Sheet 1 Filed Oct. 19, 1965 R my x w W D TT ATTORNEY May 30, 1967 D. K. SKOOG 3,32

IMPACT TOOL Filed Oct. 19, 1965 2 Sheets-Sheet 2 1 I i E50 29 J i F/G. 4

INVENTOR DONALD K. 5/(006' BY QM u) ATTORNEY United States Patent Ofiiice 3,322,208 Patented May 30, 1967 3,322,208 IMPACT TOOL Donald K. Skoog, Mountainside, N.J., assignor to lngersell-Rand Company, New York, N.Y., a corporation of New Jersey Filed Oct. 19, 1965, Ser. No. 497,982 8 Claims. (Cl. 173-123) This invention relates to impact tools and more particularly to a hydraulic impact tool. This application is a continuation-in-part of my United States patent application, Serial No. 419,898, filed December 21, 1964.

Over the years, much work has been done in the impact tool industry in efforts to develop an impact tool capable of replacing the well-known pneumatic hammer. Some of this work has resulted in devices utilizing various mechanical spring and cam mechanisms for converting rotary motion to linear impact motion. To date, spring and cam devices of this nature have only found utility in small energy transfer applications. Such mechanisms have not been satisfactory when operating at high energy levels and high frequency impact blow rates. In general, when operating at high energy levels, these prior devices have had relatively short lives, provided relatively small energy outputs, and have been relatively heavy, large and bulky.

It is the general object of the present invention to avoid and overcome the foregoing and other difficulties and objections to prior art practices by the provision of a simple impact tool for high energy transfer applications utilizing a spring and cam mechanism.

Another object of the present invention is to provide an impact tool capable of long life under operation at high frequency impact blow rates.

Still another object of the present invention is to provide an impact tool having variable energy transfer means.

Yet another object of the present invention is to provide a spring means capable of efiicient operation in a relatively small working space.

The aforesaid objects of the present invention, and other objects which will become apparent as the description proceeds are achieved by providing an impact tool with hydraulic spring means. Hammer means is operatively associated with the hydraulic spring means in an arrangement whereby energy is periodically stored in the hydraulic spring means and then abruptly released to the hammer means to operate the impact tool.

For a better understanding of the present invention reference should be had to the accompanying drawings, wherein like numerals of reference indicate similar parts throughout the several views and wherein:

FIG. 1 is an elevational view with portions cut away and shown in section of an impact tool illustrating the present invention;

FIG. 2 is a perspective view of a cam utilized in the impact tool;

FIG. 3 is a sectional view taken along the line 33 of FIG. 1; and

FIG. 4 is a fragmentary sectional view illustrating an alternative embodiment of an impact tool utilizing the spring means of the present invention.

Although the principles of the present invention are broadly applicable to all spring actuated mechanisms the present invention is particularly adapted for use in conjunction with impact tools and has been so illustrated and described.

FIG. 1 shows an impact tool having a casing 12 and a drive means, such as a standard motor 14, which may be of the hydraulic, air or electric type, disposed in the casing 12. Actuator means, such as for example, a cam assembly 16 is disposed in the casing 12 in position to be driven by the motor 14.

The cam assembly 16 has a cam driver 13 that is rotatably driven by the motor 14 through a shaft 20, as shown in FIG. 1. A cam 22 is keyed to and is driven by the cam driver 18. The cam 22 is better shown in FIG. 2 and has an end face forming a cam surface 23 of the gradually rising and abruptly dropping type whereby when the cam 22 is rotated in the direction of the cam rising slope, a cam follower 24 riding on the cam 22 is elevated to the highest point 26 of the cam 22 and then allowed to abruptly drop to the cam starting level 28. It is noted that various expedients or devices well known in the art can be employed to overcome wear problems inherent in this type of cam.

The tool 10- oontains a reciprocable hammer 29 having an upper end 30 rotatably and slidably mounted in a central cylindrical bore 31 provided in the cam 22. This construction allows the cam 22 to rotate while the hammer 29 is restrained from rotating and able to reciprocate axially.

In order to convert the rotational motion of the cam 22 into linear hammer motion, the cam follower 24 is fixed on the upper end 30 of the hammer 29, as shown in FIG. 1. If desired, the cam follower 24 can be a roller for reducing Wear and friction losses. It will now be understood that as the cam 22 is rotated it will cause the hammer 29 to reciprocate along the longitudinal axis of the impact tool 10.

In order to generate impact energy in the hammer 29, hydraulic spring means, such as a hydraulic spring assembly 36, is disposed around the hammer 29, as shown in FIG. 1. The hydraulic spring assembly 36 includes a housing 38 providing a chamber 40 filled with any essentially noncompressible fluid, such as oil or water. The hammer 29' extends through the chamber 40 and upper and lower central bores 42 and 43 provided in the housing 38. Each of the bores 42 and 43 contains seals, such as 0- rings 44 for preventing leakage of the hydraulic fluid through the bores 42 and 43. The fluid in the chamber 40 surrounds and intimately engages the length of the hammer 29 extending through the chamber 40.

The hammer 29 includes a splined portion 32 located immediately below the cam 22 and meshing with cooperating internal splines 33 provided in the upper end of the upper bore 42 of the housing 38 for preventing the hammer 29 from rotating while reciprocating in the tool 10. The lower end of the bore 31 in the cam 22 is enlarged at 34 to receive the splined portion 32 of the hammer 29 during its reciprocation without interference occurring between the hammer 29 and the cam 22.

The portion of the hammer 29 extending through the chamber 40 is arranged in two-volume sections including a small-diameter upper section 46 and a large-diameter lower section 48 with a rearwardly facing piston shoulder 49 interconnecting the upper and lower sections 46 and 48. It will now be seen that as the action of the cam 22 lifts the hammer 29 along the longitudinal axis of the impact tool 10, the rearwardly moving shoulder 49 will decrease the volume of the chamber 4i) surrounding the hammer 29. This decrease of volume within the chamber 40 will cause the hydraulic fluid to be slightly compressed.

It is well known that the so-called incompressible fluids, such as oil or water can be slightly compressed and when so compressed become storehouses of potential energy. Thus when the cam 22 raises the hammer 29 to its high point 26, the position of the hammer shown in dotted lines in FIG. 1, the hydraulic spring assembly 36 will store a large amount of potential energy acting against the shoulder 49 of the hammer 29 in the direction of the force arrows shown in FIG. 1. When the hammer 29, after being raised to the cam high point 26, is released by the cam 22, the immediate expansion of the fluid in the chamber 40 operates to push the hammer 29 longitudinally toward the tool end 54 of the impact tool 10, imparted with the full energy stored in the hydraulic spring assembly 36 to strike a blow against the anvil end 55 of a drill steel 56. Thus the high energy stored in the fluid in the chamber 40 is delivered to the drill steel 56 through the hammer 29. The drill steel 56 is slidably mounted in a conventional chuck 57.

ALTERNATIVE EMBODIMENT The alternative embodiment 58 shown in FIG. 4 contains means for varying the effect of the hydraulic spring means on the hammer 2?. This means includes a spring housing 59 having two fluid chambers 60 and 62 communicating with each other through a valved passage 64. This embodiment provides a choice of two spring rates acting on the hammer 29. It will be understood that the opening or closing of the valve 66 will change the volume of fluid subjected to the compressive action of the piston, thus changing the amount of the energy stored in the hydraulic spring assembly 26, as forexample, twice the liquid volume halves the energy stored. A change in the energy stored results in a resultant change in the spring rate thus allowing for greater flexibility in the use of the impact tool in cases where maximum spring rate output is not desirable such as when commencing an operation.

Still further alternatively a greater number of fluid compartments can be provided to further vary the tool spring rate.

Although two embodiments are illustrated and described in detail, it will be understood that the invention is not limited simply to these embodiments, but contemplate other embodiments and variations which utilize the concepts and teachings of this invention.

Having described my invention, I claim:

1. An impact tool comprising:

a housing;

a cam disposed in said housing, said cam being provided with a cam bore;

a piston slidably disposed in said cam bore;

said housing and said piston being provided'with means for allowing linear motion between said housing and said piston while preventing rotational relative motion therebetween;

said piston being provided with at least two different diameter sections, the smaller of which is located closest to said cam;

means for rotatably driving said cam;

a cam follower disposed on said piston and driven by said cam for converting the cam rotating motion to piston reciprocating linear motion;

a hydraulic tank disposed around said piston containing portions of each of said diflerent diameter sections;

said hydraulic tank being privided with essentially incompressible fluid so that when said piston is reciprocated upwards the reduction in volume of said fluid within said hydraulic tank stores energy in said fluid; and

means for imparting said energy to said piston.

2. An impact tool comprising:

a casing;

a hammer mounted for reciprocal movement within said casing;

means for raising and releasing said hammer;

means for imparting an impacting force to said hammer when said hammer is released;

said force imparting means including a first chamber substantially filled with hydraulic fluid and substantially sealed during operation of the tool;

said hammer extending into the chamber for compressing said fluid when said hammer is raised and said hydraulic fluid adapted to impart its stored energy to said hammer when said hammer is released.

3. The impact tool of claim 2 wherein said raising and releasing means includes follower means mounted on said hammer, cam means associated with said follower and means for rotating said cam.

4. The impact tool of claim 3 wherein said cam is coaxial with said hammer and said hammer extends through said first chamber and said cam, said hammer having a reduced diameter portion to provide a shoulder within said chamber.

5. The impact tool of claim 4 wherein said hammer is non-rotative with respect to said cam.

6. The impact tool of claim 2 further including means for varying the impacting force imparted to said hammer.

7. The impact tool of claim 6 wherein said varying means includes at least one additional chamber substantially filled with hydraulic fluid and being interconnected with said first chamber by a valved passage.

8. The impact tool of claim 7 wherein said means for raising and releasing said hammer includes a follower mounted on said hammer, cam means associated with said follower and means for rotating said cam.

References Cited UNITED STATES PATENTS 650,088 5/1900 Hoag 173120 2,776,539 1/1957 Pearson 173-123 2,794,621 6/1957 Beeson 173-120 3,162,252 12/1964 Cobi l73-120 FRED C. MATTERN, JR., Primary Examiner.

L. P. KESSLER, Assistant Examiner. 

1. AN IMPACT TOOL COMPRISING: A HOUSING; A CAM DISPOSED IN SAID HOUSING, SAID CAM BEING PROVIDED WITH A CAM BORE; A PISTON SLIDABLY DISPOSED IN SAID CAM BORE; SAID HOUSING AND SAID PISTON BEING PROVIDED WITH MEANS FOR ALLOWING LINEAR MOTION BETWEEN SAID HOUSING AND SAID PISTON WHILE PREVENTING ROTATIONAL RELATIVE MOTION THEREBETWEEN; SAID PISTON BEING PROVIDED WITH AT LEAST TWO DIFFERENT DIAMETER SECTIONS, THE SMALLER OF WHICH IS LOCATED CLOSEST TO SAID CAM; MEANS FOR ROTATABLY DRIVING SAID CAM; A CAM FOLLOWER DISPOSED ON SAID PISTON AND DRIVEN BY SAID CAM FOR CONVERTING THE CAM ROTATING MOTION TO PISTON RECIPROCATING LINEAR MOTION; A HYDRAULIC TANK DISPOSED AROUND SAID PISTON CONTAINING PORTIONS OF EACH OF SAID DIFFERENT DIAMETER SECTIONS; SAID HYDRAULIC TANK BEING PROVIDED WITH ESSENTIALLY INCOMPRESSIBLE FLUID SO THAT WHEN SAID PISTON IS RECIPROCATED UPWARDS THE REDUCTION IN VOLUME OF SAID FLUID WITHIN SAID HYDRAULIC TANK STORES ENERGY IN SAID FLUID; AND MEANS FOR IMPARTING SAID ENERGY TO SAID PISTON. 